System and method for optical multiplexing and/or demultiplexing

ABSTRACT

Improved methods and systems for routing and aligning beams and optical elements in an optical device include a multiplexing device and/or a demultiplexing device, which includes an optical alignment element (OAE). The OAE can be configured to substantially compensate for the cumulative alignment errors in the beam path. The OAE allows the optical elements in a device, other than the OAE, to be placed and fixed in place without substantially compensating for optical alignment errors. The OAE is inserted into the beam path and adjusted. This greatly increases the ease in the manufacturing of optical devices, especially for devices with numerous optical elements, and lowers the cost of manufacturing. The multiplexing and/or demultiplexing device can reside within a standard small form factor, such as a GBIC. The devices fold the paths of the traversing beams with a geometry which allows a small package.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of co-pending U.S. patentapplication Ser. No. 09/916,624 entitled “Optical Alignment ElementMethod,” filed on Jul. 27, 2001. This application also claims priorityfrom Provisional Application Serial No. 60/350,407 entitled “System andMethod for Optical Multiplexing and/or Demultiplexing,” filed on Jan.18, 2002.

FIELD OF THE INVENTION

The field of the invention relates to routing and alignment of beams inan optical system and more particularly to systems and methods for wavedivision multiplexing and/or demultiplexing for a fiber optic network.

BACKGROUND OF THE INVENTION

Precision alignment of an optical beam through optical devices andsystems may pose a variety of challenges. Devices may contain multipleoptical elements, each having an associated alignment error that must becorrected. For instance, in optical multiplexing, a number of beams fromdifferent sources may need to be aligned with the tip of an opticalfiber and each beam path may have different alignment error due toinaccuracies inherent in the fabrication and placement of opticalcomponents used in the device. One approach to alignment involvesindividually aligning the beam source and target, as well as eachoptical component, in multiple dimensions as they are placed.Manipulating multiple interdependent components may be complex and timeconsuming, and may be difficult due to the size and configuration of thesystem. In addition, aligning the source or target can be difficult,since it may be electrically powered and have unique mounting ormonitoring requirements. Also, the source or target may be the largestelement and allowing for movement during alignment may increase the formfactor of the entire device.

One example of an optical system requiring alignment is an opticalnetwork carrying multiple channels of information on an optical fiber.The information on each channel may be carried in an optical signalwithin a defined range of wavelengths that can be separated from theother channels. Wavelength division multiplexing (WDM) may be used toadd a channel to the fiber or to combine and add a number of channels tothe fiber. Wavelength division demultiplexing (WDDM) may be used toseparate channels from the fiber.

One approach for WDDM is to use dispersion to separate the channels inan optical signal. However, it may be difficult to align the multipledispersed channels with target fibers or other optical componentsintended to receive the separate channels. Among other things,temperature changes may cause thermal expansion or contraction ofcomponents that result in alignment error. Moreover, a long beam pathmay be required to achieve sufficient physical separation of thechannels, which exacerbates alignment errors and may place limitationson the minimum size for the system.

Another approach involves using wavelength filters to separateindividual channels from the incoming signal. In order to providealignment, the signals may be carried to and from the filters by opticalfibers coupled to the filters. However, a series of fiber loops may berequired to route the signals to and from the filters, which can placelimitations on the minimum size of the system. For instance, a WDDM mayinterface with a plurality of receive optical assemblies (ROSAs) whichuse a standard form factor, such as a GigaBaud Interface Converter(GBIC) form factor.

The GBIC specification was developed by a group of electronicmanufacturers in order to arrive at a standard form factor transceivermodule for use with a wide variety of serial transmission media andconnectors. The specification defines the electronic, electrical, andphysical interface of a removable serial transceiver module designed tooperate at Gigabaud speeds. A GBIC provides a pluggable communicationmodule which may be inserted and removed from a host or switch chassiswithout powering off the receiving socket. The GBIC form factor definesa module housing which includes a first electrical connector forconnecting the module to a host device or chassis. This first electricalconnector mates with a standard socket, which provides the interfacebetween the host device printed circuit board and the module. The GBICmodule itself is designed to slide into a mounting slot formed withinthe chassis of a host device.

Each GBIC may be coupled to an optical fiber loop that feeds into afilter. The fiber loops and other components may be included in ahousing with a form factor much larger than the GBIC. Accordingly, onepossible design for a 4-to-1 WDDM system would use four GBICs (one forreceiving each channel) and a separate housing for the WDDM. In manyapplications, however, it may be desirable to provide a much morecompact design, such as a WDM or WDDM that can be configured to fitwithin a single GBIC or smaller form factor.

Accordingly, there exists a need for improved methods and systems forrouting and aligning beams and optical elements in an optical device,such as a WDM, WDDM or other optical device.

SUMMARY OF THE INVENTION

Improved methods and systems for routing and aligning beams and opticalelements in an optical device, such as a WDM, WDDM or other opticaldevice, are provided in accordance with embodiments of the presentinvention.

One aspect of the present invention provides an optical alignmentelement (OAE) that can be configured to substantially compensate for thecumulative alignment errors in the beam path. The OAE allows the opticalelements in a device, other than the OAE, to be placed and fixed inplace without substantially compensating for optical alignment errors.The OAE is inserted into the beam path and adjusted. This greatlyincreases the ease in the manufacturing of optical devices, especiallyfor devices with numerous optical elements, and lowers the cost ofmanufacturing.

Another aspect of the present invention provides a compact multiplexerand/or demultiplex configuration which allows for the alignment ofmultiple folded beam paths to combine or separate optical channels. Inone embodiment, a number of filters and mirrors are mounted on a core toroute the beams. This aspect of the invention can be used to provide avery compact design and to permit flexibility in the placement ofoptical components. For instance, active components (such as lasers oroptical receivers) may be positioned so that the electrical leads passthrough the bottom of the device for convenient mounting to a printedcircuit board, while an optical fiber which transmits or receives theoptical signal from the network passes through the side of the device.The flexibility in routing, folding and aligning optical beams allowsthe components to be positioned conveniently for interfacing to externaldevices rather than being constrained by the alignment requirements ofthe device.

Another aspect of the present invention uses a compact form factor for amultiplexing device and/or demultiplexing device. The form factor may bea standard form factor typically used for a pluggable communicationsmodule which interfaces between serial transmission media and a hostsocket. These form factors may be defined for hot pluggable devices,such as receive optical sub-assemblies (ROSAs) and transmit opticalsub-assemblies (TOSAs) in optical systems. Examples of these formfactors include the GBIC form factor, the small form factor (SFF) andthe small form pluggable (SFP) form factor. Aspects of the presentinvention provide for a compact multiplexer and/or demultiplexer usingone of these form factors or an external housing and socket that iscompatible with one of these form factors. This aspect of the inventioncan be used to provide a compact multiplexer and/or demultiplexer thatcan be inserted or removed from host sockets as part of a single modulecompatible with current host sockets used for ROSAs and TOSAs andthereby provide substantially more functionality with the sameconvenience.

In an exemplary embodiment, a multiplexing device is provided, whichcomprises: a plurality of components, wherein each component provides abeam with a channel in a range of wavelengths; a filter associated witheach channel, wherein each filter is configured to select the beam forthe respective channel; an output to receive the beam for each componentafter the beam traverses the respective filter; and an optical alignmentelement (OAE) associated with each channel, wherein the OAE can beconfigured to provide at least two directional changes in the path ofthe beam. In addition, in some embodiments, the path of the beam inputto the OAE may be non-coplanar with the path of the beam output from theOAE.

In another exemplary embodiment, a demultiplexing device is provided,which comprises: an input, wherein the input provides a beam with aplurality of channels, each channel in a range of wavelengths; a filterassociated with each channel, wherein each filter is configured toselect the beam for the respective channel; a plurality of outputsassociated with each channel, wherein each output receives the beam forthe respective channel after the beam traverses the respective filter;and an OAE associated with each channel, wherein the OAE can beconfigured to provide at least two directional changes in the path ofthe beam. In addition, in some embodiments, the path of the beam inputto the OAE may be non-coplanar with the path of the beam output from theOAE.

In another exemplary embodiment, a method for multiplexing a pluralityof beams, each beam including a channel in a range of wavelengths isprovided, which comprises the steps of: (a) traversing the plurality ofbeams through a plurality of filters, each filter associated with one ofthe channels, wherein each filter is configured to select the beam forthe respective channel; (b) redirecting a path of each filtered beamusing an OAE, wherein the OAE can be configured to provide at least twodirectional changes in the path of the filtered beam; and (c) outputtingeach filtered and redirected beam to a receiver. In addition, in someembodiments, the path of the beam input to the OAE may be non-coplanarwith the path of the beam output from the OAE.

In another exemplary embodiment, a method for demultiplexing an opticalsignal, the optical signal including a plurality of channels in a rangeof wavelengths, is provided, which comprises the steps of: (a)traversing the optical signal through a plurality of filters, eachfilter associated with each channel, wherein each filter is configuredto select the beam for the respective channel; (b) transmitting eachchannel after the beam traverses the respective filter; and (c)redirecting a path of each transmitted beam using an OAE, wherein theOAE can be configured to provide at least two directional changes in thepath of the transmitted beam. In addition, in some embodiments, the pathof the beam input to the OAE may be non-coplanar with the path of thebeam output from the OAE.

In another exemplary embodiment, a frame is provided for assembling andaligning a multiplexer and/or demultiplexer. The frame forms a firstplurality of openings and/or mounting surfaces, each configured toreceive a light source or output element associated with a channel in amultiplexer or demultiplexer. The light source or output element may befixed in place using hot wicking, solder, a press fit or interferencefit or other method. The frame forms a second plurality of openingsand/or mounting surfaces, each configured to receive a filter moduleassociated with one of the channels to select the beam in the range ofwavelengths for the respective channel. The filters may be fixed inplace using hot wicking, solder, a press fit or interference fit orother method. The frame forms a third plurality of openings, eachconfigured to receive an optical element associated with each channel ina position transverse to the beam for the respective channel. Theopening for each optical element may be sized to allow the opticalelement to be moved within such opening for alignment prior to beingfixedly mounted to the frame. The frame may be provided in exemplaryembodiments by a core that fits into a chassis or by a unitary framewith holes and angled surfaces for inserting and/or mounting the opticalcomponents. In some embodiments additional optical components, such asmirrors or lenses, may be mounted to the frame.

Exemplary embodiments of the present invention may use one or more ofthe aspects described above, alone, or in combination.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates an embodiment of WDM and WDDM devices in a GBIC formfactor.

FIG. 1B illustrates a block diagram of an embodiment of a multiplexingdevice.

FIG. 1C illustrates a block diagram of an embodiment of a demultiplexingdevice.

FIG. 2A illustrates a block diagram of another embodiment of amultiplexing device.

FIG. 2B illustrates a block diagram of another embodiment of ademultiplexing device.

FIGS. 2C-2F illustrate a top isometric, bottom isometric, top, and sideview, respectively, of an embodiment of a core of a device.

FIGS. 3A-3D illustrate an isometric, top, front, and side view,respectively, of an embodiment of the device with an embodiment of thecore.

FIG. 4 illustrates a top, side, and cross-sectional orthogonal views ofthe prism as the OAE.

FIG. 5 illustrates an isometric view of the prism as the OAE.

FIG. 6 illustrates the positioning of the beam with a prism movement inthe x-direction.

FIG. 7 illustrates the positioning of the beam with a prism movement inthe θ_(x) direction.

FIG. 8 illustrates the positioning of the beam with a prism movement inthe z-direction.

FIG. 9 illustrates the positioning of the beam with a prism movement inthe θ_(z) direction.

FIG. 10 illustrates the positioning of the beam with a prism movement inthe prism y-direction and in the prism θ_(y) (θ_(yp)) direction.

FIGS. 11A-11E illustrate a top isometric, bottom isometric, top, bottom,and side views, respectively, of another embodiment of a core of thedevice.

FIGS. 12A-12D illustrate a top isometric, bottom isometric, top, andbottom views, respectively, of an embodiment of the device with anotherembodiment of the core.

FIGS. 13A-13C illustrate an isometric, top, and front views,respectively, of an embodiment of a chassis for the device.

FIGS. 14A-14C illustrate an isometric, top, and side view of a bowtieconfiguration of a hole for adjusting the OAE in the chassis for thedevice.

FIGS. 15A-15E illustrate two top isometric views, two bottom isometricviews, and a side view, respectively, of a graduation cap for adjustingthe OAE in the chassis for the device.

FIG. 15F is a block diagram of an exemplary system for aligning an OAEor other optical components in accordance with embodiments of thepresent invention.

FIG. 15G is a flow chart of an exemplary hill climb alignment method inaccordance with an embodiment of the present invention.

FIG. 15H is a flow chart of an exemplary fine alignment method inaccordance with an embodiment of the present invention.

FIGS. 16A-16C illustrate an isometric, side, and top views,respectively, of a system for allowing the adjustment of the OAE andcoupling to the chassis for the device.

FIGS. 17A-17D illustrate a top, top isometric, top cross-sectional, andside cross-sectional views, respectively, of another system for allowingthe adjustment of the OAE and coupling to the chassis for the device.

FIGS. 17E-17F illustrate a top and side cross-sectional view,respectively, of yet another system for allowing the adjustment of theOAE and coupling to the chassis for the device.

FIGS. 17G-17H illustrate a top and side cross-sectional view,respectively, of yet another system for allowing the adjustment of theOAE and coupling to the chassis for the device.

FIGS. 18A-18B illustrate side views of yet another system for allowingthe adjustment of the OAE and coupling to the chassis for the device.

FIG. 18C illustrates an embodiment of the device with fiber support.

FIGS. 19A-19C illustrate a top isometric, bottom isometric, and topviews, respectively, of yet another embodiment of a core for a device.

FIGS. 20A-20E illustrate a top isometric, bottom isometric, top, front,and side views, respectively, of an embodiment of the device with yetanother embodiment of the core.

FIGS. 21A-21E illustrate a top isometric, bottom isometric, top, front,and side views, respectively, of yet another embodiment of a core for adevice.

FIGS. 22A-22D illustrate a top isometric, bottom isometric, top, andside views, respectively, of another embodiment of the device with theanother embodiment of the core.

FIGS. 23A-23E illustrate a top isometric, bottom isometric, top, front,and side views, respectively, of an embodiment of a chassis for thedevice.

FIG. 24 illustrates a front view of an embodiment of the device withouta core.

FIGS. 25A-25B illustrate a top isometric and bottom isometric views,respectively, of a front plate of the embodiment of the device withoutthe core.

FIGS. 26A-26B illustrate a back and front views, respectively, of theembodiment of the device without the core.

DETAILED DESCRIPTION

Improved methods and systems for routing and aligning beams and opticalelements in an optical device are described below. The followingdescription is presented to enable one of ordinary skill in the art tomake and use the invention and is provided in the context of a patentapplication and its requirements. Various modifications to the preferredembodiment will be readily apparent to those skilled in the art and thegeneric principles herein may be applied to other embodiments. Thus, thepresent invention is not intended to be limited to the embodiment shownbut is to be accorded the widest scope consistent with the principlesand features described herein.

FIG. 1A illustrates an embodiment of WDM and WDDM devices in a GBIC formfactor. The module 150 comprises the GBIC housing 152, which is part ofthe GBIC form factor, as defined by the GBIC specification. The module150 may also comprise a connector which is compatible with theelectrical interface defined by the GBIC specification and may be hotpluggable into a host socket. Within the GBIC housing 152 is a WDMdevice 154 and a WDDM device 156. Alternatively, multiple WDM devices,multiple WDDM devices, a combination of WDM and WDDM devices, a singleWDM, or a single WDDM may reside within the GBIC housing 152. The WDM orWDDM devices 154 and 156 may support any number of channels, includingbut not limited to 2, 4, 8, 16, 32, 64, and 128 channels. A “channel”,as used in this specification, is a path through which signals may flow.A channel may include a range of wavelengths of light. “Light” refers toany wavelength, including but not limited to non-visible wavelength ofradiation, such as infrared. In this embodiment, the module 150 alsocomprises a fiber support 158. The function of the fiber strain relief158 will be described below with FIG. 18C.

Other form factors may be used in connection with embodiments of thepresent invention. Various form factors allow for one or more TOSAs orROSAs to be provided between optical fibers in an optical network and asocket for a host device or chassis. The form factors may be adapted foruse in a hot pluggable environment where TOSAs and/or ROSAs may be addedor removed from optical networking equipment without powering off thereceiving socket. For instance, the GBIC form factor was developed inorder to arrive at a standard small form factor transceiver module foruse with a wide variety of serial transmission media and connectors.Other form factors include a small form factor (SFF), a small formfactor pluggable (SFP), Xenpak, XPAK, XGP, XGP2, XFP or any otherstandard or non-standard form factor. Exemplary embodiments of the WDMdevice 154 and the WDDM device 156 are described below. In exemplaryembodiments of the present invention, WDM and/or WDDM modules may beprovided within a housing conforming to any of the above or other formfactors. For instance, a WDM or WDDM module could replace the ROSA orTOSA normally embedded in the housing. The housing conforms to the formfactor by providing external features which allow the housing to bemounted on a rack or other system adapted for devices with therespective form factor, such as external dimensions and surface featureswhich allow the housing to fit in a cage, slide onto rails, attach to aclip or otherwise attach as required for the respective form factor. Thehousing may be considered to conform to the form factor even if it doesnot provide an electrical interface specified by the respectivestandard. For instance, some embodiments of the present invention may bepassive and use optical fibers to provide inputs and outputs rather thanactive lasers and receivers. These embodiments may not provide anelectrical connector interface, but may conform to the form factor formounting purposes. Some embodiments of the present invention may alsoprovide an electrical connector and an electrical interface compatiblewith any of the standards described above or may use a non-standardelectrical interface.

Aspects of the present invention allow an entire WDM or WDDM (or acombination of one or more of the foregoing) to be conveniently providedwithin various small form factors. Thus, a WDM, WDDM or combination maybe added or removed from a host device using only a single socket andwithout powering down the socket. This is in contrast to a conventionalsystem that might use multiple GBIC or other modules (containing onlyROSAs and TOSAs) in multiple sockets to provide transmitters and/orreceivers for a WDM or WDDM.

The WDM device 154 can be a Coarse WDM (CWDM) or a Dense WDM (DWDM)device. The WDDM device 156 can be a Coarse WDDM (CWDDM) or a Dense WDDM(DWDDM) device. In an exemplary CWDM (or CWDDM) embodiment, the channelsmay for instance be divided among the following wavelengths: 1511 nm,1531 nm, 1551 nm, and 1571 nm; 1471 nm, 1491 nm, 1511 nm, 1531 nm, 1551nm, 1571 nm, 1591 nm, and 1611 nm; 1481 nm, 1501 nm, 1521 nm, 1541 nm,1561 nm, 1581 nm, 1601 nm, and 1621 nm; or 1461 nm, 1481 nm, 1501 nm,1521 nm, 1541 nm, 1561 nm, 1581 nm, 1601 nm. In an exemplary DWDM (orDWDDM) embodiment, the channels may for instance be divided among thefollowing wavelength spacings: 400 GHz, 200 GHz, 100 GHz, and 50 GHz.

FIG. 1B illustrates a block diagram of an embodiment of a multiplexingdevice. The device 160 can use passive inputs and outputs (such asoptical fibers) or active inputs and outputs (such as lasers andphotosensors) or a combination of both. In this embodiment, the device160 is a four-channel device, with four beam paths, although any numberof beam paths may be supported. In the first beam path, the device 160comprises a first light source 162 a, a first OAE 164 a, a first filter166 a, and an output element 168. In the second beam path, the device160 comprises a second light source 162 b, a second OAF 164 b, a secondfilter 166 b, and the output element 168. In the third beam path, thedevice 160 comprises a third light source 162 c, a third OAE 164 c, athird filter 166 c, and the output element 168. In the fourth beam path,the device 160 comprises a fourth light source 162 d, a fourth OAF 164d, a fourth filter 166 d, and the output element 168. In thisembodiment, any of the filters 166 a-166 d can be a reflective filter,or some other optical element which allows the channels from the beampaths to be multiplexed.

The light sources 162 a-162 d may be a transmitter, such as a laser, alaser can package, an array of can packages, a wave guide, a single- ormulti-mode optical fiber, a light emitting diode, an array of lightemitting diodes, an optical signal modulator, an optical network, anoptical switch, or any other optical systems or subsystems whichtransmit or emit light. The output element 168 is some type of receiver,such as a single- or multi-mode optical fiber, detector, detector canpackage, nozzle, lens, focusing optic, collimator, waveguides, receiversor any other passive or active optical system or subsystem for receivingor detecting light. The nozzle can be configured to accept any type ofconnector, such as SC, FC, ST, LC, MU, or E2000, with any type offinish, such as PC, UPC<SPC, or APC. The first light source 162 a emitsa beam which traverses through the first OAE 164 a. The beam exits thefirst OAE 164 a to the first filter 166 a. The first filter 166 aselects a first range of wavelengths, λ₁, to traverse to the outputelement 168. The manner in which the first filter selects the firstrange of wavelengths depends upon the type of filter. If the firstfilter is a transmissive filter, a range of wavelengths (including atleast the selected wavelengths) pass through the filter and otherwavelengths are reflected. The range of wavelengths that passes throughthe filter may be wider than the selected wavelengths for the particularchannel, but is narrow enough to avoid overlap and interference withother channels. If the filter is a transmissive grating or dispersiveoptic, the light is diffracted or dispersed at different anglesdepending upon wavelength. The desired wavelength is selected byaligning a range of wavelengths (including at least the selectedwavelengths) from the grating or optic with the desired output path. Ifthe filter is a reflective filter, a range of wavelengths (including atleast the selected wavelengths) reflects from the filter and otherwavelengths pass through the filter. If the filter is a reflectivegrating or optic, the light is reflected at different angles dependingupon wavelength. The desired wavelength is selected by aligning a rangeof wavelengths (including at least the selected wavelengths) from thereflective grating or optic with the desired output path.

The first light source 162 a, the first OAE 164 a and the first filter166 a are considered to be associated with first channel (provided bythe first range of wavelengths). These components provide, align andfilter the beam carrying the first channel in order to supply it to theoutput element 168. Similarly, second, third and fourth sets of lightsources, OAEs and filters are provide to supply a second, third andfourth channel to the output element 168 as described below, and therebyprovide a multiplexed output beam.

The second light source 162 b emits a beam which traverses through thesecond OAE 164 b to the second filter 166 b. The second filter 166 bselects a second range of wavelengths, λ₂, to traverse to the outputelement 168. λ₁ is transmitted through the second filter 166 b. Thethird light source 162 c emits a beam which traverses through the thirdOAE 164 c to the third filter 166 c. The third filter 166 c selects athird range of wavelengths, λ₃, to traverse to the output element 168.λ₁, λ₂ are transmitted through the third filter 1606 c. The fourth lightsource 162 d emits a beam which traverses through the fourth OAE 164 dto the fourth filter 166 d. The fourth filter 166 d selects a fourthrange of wavelengths, λ₄, to traverse to the output element 168. λ₁, λ₂,λ₃ are transmitted through the fourth filter 166 d. A compositemultiplexed beam comprising λ₁, λ₂, λ₃, and λ₄ is transmitted to theoutput element 168.

FIG. 1C illustrates a block diagram of an embodiment of a demultiplexingdevice. The demultiplexing device 170 may comprise a similar structureas the multiplexing device 160 but differs in operation. In thedemultiplexing device, a composite beam is received at input element169. A range of wavelengths (λ₁, λ₂, λ₃, or λ₄) is selected by filters166 a-d, respectively and directed to OAE 164 a-d respectively. The OAEsalign the beams with the respective output element 163 a-d. The inputelement 169 is some type of transmitter, such as a laser, a laser canpackage, an array of can packages, a waveguide, a single- or multi-modeoptical fiber, a light emitting diode, an array of light emittingdiodes, an optical signal modulator, an optical network, an opticalswitch or any other optical systems or subsystems which transmit or emitlight. The output elements 163 a-163 d are each some type of receiver,such as a single- or multi-mode optical fiber, detector, detector canpackage, nozzle, lens, focusing optic, collimator, waveguides or anyother passive or active optical system or subsystem for receiving ordetecting light. The nozzle can be configured to accept any type ofconnector, such as SC, FC, ST, LC, MU, or E2000, with any type offinish, such as PC, UPC, SPC, or APC.

The input element 169 emits a multiplexed beam comprising λ₁, λ₂, λ₃,and λ₄ and transmits it to the fourth filter 166 d. The fourth filter166 d selects λ₄ to traverse to the fourth OAE 164 d. λ₄ traverses thefourth OAE 164 d and is transmitted to the fourth output element 163 d.The remaining wavelengths, λ₁, λ₂, and λ₃, are transmitted from thefourth filter 166 d to the third filter 166 c. The third filter 166 cselects λ₃ to traverse to the third OAE 164 c. λ₃ traverses the thirdOAE 164 c and is transmitted to the third output element 163 c. Theremaining wavelengths, λ₁ and λ₂, are transmitted from the third filter166 c to the second filter 166 b. The second filter 166 b selects λ₂ totraverse to the second OAE 164 b. λ₂ traverses the second OAE 164 b andis transmitted to the second output element 163 b. The remainingwavelength, λ₁, is transmitted from the second filter 166 b to the firstfilter 166 a. The first filter 166 a causes λ₁ to traverse to the firstOAE 164 a. λ₁ traverses the first OAE 164 a and is transmitted to thefirst output element 163 a. Accordingly, each channel is associated witha filter, OAE and output element which select, align and output therespective channel.

The multiplexing device 160 and demultiplexing device 170 are describedfurther in the Co-Pending U.S. patent application entitled, “OpticalAlignment Element Method”, Ser. No. 09/916,624 filed on Jul. 27, 2001 bythe assignee of the present application. Applicants hereby incorporatethis patent application by reference.

FIG. 2A illustrates a block diagram of another embodiment of amultiplexing device. The device 100 comprises a core 102 that mayinclude a plurality of filters 104 a-104 d. In this embodiment, thefilters may be transmissive filters which select a channel by allowingit to pass through the filter while other channels are reflected,although embodiments with different filters may be used as well. In thisembodiment and other exemplary embodiments, the angle of incidence ofthe light beam on the filter may be optimized to enhance the filter'sability to select the desired channel. The angle of incidence is theangle between the light beam and a line that is perpendicular to theface of the filter. Accordingly, a light beam that is perpendicular tothe face of the filter would have a zero degree angle of incidence. Inthe embodiment of FIG. 2A and other exemplary embodiments, the angle ofincidence may be about ten degrees. In other embodiments, differentangles may be selected to enhance performance of the particular filtersbeing used.

In FIG. 2A, each filter 104 a-104 d transmits light of a particularwavelength range while reflecting other wavelengths. For example, eachfilter 104 a-104 d can be either band filters or edge filters, arrangedin the appropriate order. Each filter 104 a-104 d is optically coupledto an optical alignment element (OAE) 106 a-106 d, which in turn isoptically coupled to a light source 108 a-108 d. Each of the lightsources 108 a-108 d transmits a respective channel in a particular rangeof wavelengths. For example, light source 108 d emits a beam whichincludes wavelengths λ₄ to the OAE 106 d, which redirects λ₄ to thefilter 104 d. Filter 104 d transmits λ₄ to the filter 104 c. In otherembodiments, filter 104 d can be omitted or replaced with anon-filtering optic. Light source 108 c emits a beam which includeswavelengths λ₃ to the OAE 106 c, which redirects λ₃ to the filter 104 b.Filter 104 c also reflects λ₄ toward filter 104 b. Light source 108 bemits a beam which includes wavelengths λ₂ to the OAE 106 b, whichredirects λ₂ to the filter 104 a. Filter 104 b also reflects λ₃-λ₄toward filter 104 a. Light source 108 a emits a beam which includeswavelengths λ₁ to the OAE 106 a, which redirects λ₁ to the outputelement 110. Filter 104 a also reflects λ₂-λ₄ to the output element 110.In this manner, a composite beam composed of λ₁, λ₂, λ₃, and λ₄ isoutput to the output element 110.

The light sources 108 a-108 d may be transmitters which transmit,convey, carry, or guide light. In some embodiments, the transmitters maybe active transmitters such as lasers, laser can packages, lightemitting diodes, optical signal modulators, or other types of activetransmitters. In some embodiments, the transmitters may be passivetransmitters such as waveguides, single- or multi-mode optical fibers,or other types of passive transmitters. The filters 104 a-104 d can betransmissive filters, transmissive gratings, or any other dispersive,refractive or reflective optics. The filters 104 a-104 d can reflectlight either from its front face or back face. The output element 110 isa target for the multiplexed channels and provides an output from theWDM housing for the combined beam. Output element 110 can be a receiversuch as a single- or multi-mode optical fiber, a detector, a detectorcan package, a demultiplexer, a waveguide, a nozzle, or any otheroptical systems or subsystems for receiving or detecting light. Thenozzle can be configured to accept any type of connector, such as SC,FC, ST, LC, MU, or E2000, with any type of finish, such as PC, UPC, SPC,or APC.

FIG. 2B illustrates a block diagram of another embodiment of ademultiplexing device. The demultiplexing device 150 may comprise asimilar structure as the multiplexing device 100 but differs inoperation. In the demultiplexing device 150, a composite beam isprovided by input element 111. A range of wavelengths (λ₁, λ₂, λ₃, andλ₄) is selected by filters 104 a-d respectively and directed to OAEs 106a-d respectively. The OAEs align the beams with the respective outputelement 109 a-d. For example, assume that a composite beam ofmultiplexed light from input element 111 comprises four channels, λ₁-λ₄.Filter 104 a transmits λ₁ to the OAE 106 a while reflecting λ₂-λ₄ to thefilter 104 b. The OAE 106 a redirects λ₁ to output element 109 a. Thefilter 104 b transmit λ₂ to the OAE 106 b while reflecting λ₃-λ₄ to thefilter 104 c. The OAE 106 b redirects λ₂ to output element 109 b. Thefilter 104 c transmits λ₃ to the OAE 106 c while reflecting λ₄ to thefilter 104 d. The OAE 106 c redirects λ₃ to output element 109 c. Thefilter 104 d transmits λ₄ to the OAE 106 d. In other embodiments, filter104 d can be omitted or replaced by a non-filtering optic. The OAE 106 dredirects λ₄ to output element 109 d. In this manner, a multiplexedlight is separated into its component channels. Light may be reflectedfrom each filter 104 a-104 d either from its back or front face.

The output elements 109 a-109 d are targets for the channels from amultiplexed light and provide outputs from the WDDM housing for thechannels. The output elements 109 a-109 d can comprise receivers such ascollimators, waveguides, single- or multi-mode optical fibers,detectors, detector can packages, receivers or other optical systems orsubsystems for receiving or detecting light. The filters 104 a-104 d canbe transmissive filters, transmissive gratings, or any other dispersive,refractive or reflective optics configured to select the desiredwavelengths. The filters 104 a-104 d can reflect light either from itsfront face or back face. The input element 111 can be a source of amultiplexed light, such as a transmitter, and provides an input into theWDDM housing. In some embodiments, the transmitter may be an activetransmitter such as a laser, a laser can package, an array of canpackages, a light emitting diode, an array of light emitting diodes, anoptical signal modulator, an optical network, an optical switch or anyother optical systems or subsystems for transmitting or emitting light.In some embodiments, the transmitter may be a passive transmitter suchas a waveguide, a single- or multi-mode optical fiber, or other type ofpassive transmitter. In other embodiments of the invention, more orfewer channels may be included in the device. Additional channels can beadded to or subtracted from the devices 100 and 150 by removing oradding additional filters, OAE's, and components for the additionalchannels as required.

FIGS. 2C-2F illustrate a top isometric, bottom isometric, top, and sideview, respectively, of an embodiment of a core that may be used with amultiplexing device or demultiplexing device, such as those described inconnection with FIGS. 2A and 2B. Core 200 has a prismatic shape and iscomposed of an optically transmissive material such as BK7 fused siliconor any other transparent glass or crystalline material that willtransmit the light of interest. The core 200 comprises three side faces202, 204, 206, and two end faces 208, 210. The core 200 also comprises acut face 212. The function of the cut face 212 will be described below.

FIGS. 3A-3D illustrate an isometric, top, front, and side view,respectively, of an embodiment of a multiplexing device including anembodiment of the core. In this embodiment, the multiplexing device useslight sources 108 a-d that are passive. The filters 104 a-104 d arecoupled to the side faces 202 and 204 of the core 200. A first mirror302 is coupled to the cut face 212, and a second mirror 306 is coupledto the side face 206. The OAE's 106 a-106 d are then placed proximate tothe core 200 so that they are optically coupled to their respectivefilters 104 a-104 d.

Light source 108 d transmits or emits λ₄ to the OAE 106 d, whichredirects λ₄ to the filter 104 d. Filter 104 d transmits λ₄ to thesecond mirror 306. The second mirror 306 reflects λ₄ to the filter 104c. Light source 108 c transmits or emits λ₃ to the OAE 106 c, whichredirects λ₃ to the filter 104 c. Filter 104 c transmits λ₃ to thesecond mirror 306 and also reflects λ₄ to the second mirror 306. Thesecond mirror 306 in turn reflects λ₃-λ₄ to the filter 104 b. Lightsource 108 b transmits or emits λ₂ to the OAE 106 b, which redirects λ₂to the filter 104 b. Filter 104 b transmits λ₂ to the second mirror 306also reflects λ₃-λ₄ to the second mirror 306. The second mirror 306 inturn reflects λ₂-λ₄ to the filter 104 a. Light source 108 a transmits oremits λ₁ to the OAE 106 a, which redirects λ₁ to the filter 104 a.Filter 104 a transmits λ₁ to the second mirror 306 and also reflectsλ₂-λ₄ to the second mirror 306. The second mirror 306 in turn reflectsλ₁-λ₄ to the first mirror 302, which in turn reflects λ₁-λ₄ into theoutput element 304. In this embodiment, a portion of the core 200 is cutto create the cut face 212 with the appropriate angle to ensure thatlight reflects off of the first mirror 302 at the desired angle. In thismanner, λ₁, λ₂, λ₃, and λ₄ are multiplexed into the same output element304.

A similar structure may be used for a demultiplexing device. For ademultiplexing device, the light sources 108 a-d and output element 304in FIGS. 3A-D are replaced with four output elements and an inputelement, respectively. Multiplexed light with channels λ₁-λ₄ is providedby the input element (which may be located at the position indicated at304 in FIGS. 3A-D) to the first mirror 302. The first mirror 302reflects the light toward the second mirror 306, which in turn reflectsthe light to the filter 104 a. In this embodiment, a portion of the core200 is cut to create the cut face 212 with the appropriate angle toensure that light hits the filters 104 a-104 d at the desired angles.Filter 104 a transmits λ₁ to the OAE 106 a while reflecting λ₂-λ₄ to thesecond mirror 306. The OAE 106 a redirects λ₁ to the first outputelement (which may be located at the position indicated at 108 a inFIGS. 3A-D), while the second mirror 306 reflects λ₂-λ₄ to the filter104 b. The filter 104 b transmit λ₂ to the OAE 106 b while reflectingλ₃-λ₄ to the second mirror 306. The OAE 106 b redirects λ₂ to the secondoutput element (which may be located at the position indicated at 108 bin FIGS. 3A-D), while the second mirror 306 reflects λ₃-λ₄ to the filter104 c. The filter 104 c transmits λ₃ to the OAE 106 c while reflectingλ₄ to the second mirror 306. The OAE 106 c redirects λ₃ to the thirdoutput element (which may be located at the position indicated at 108 cin FIGS. 3A-D), while the second mirror 306 reflects λ₄ to the filter104 d. The filter 104 d transmits λ₄ to the OAE 106 d. The OAE 106 dredirects λ₄ to the fourth output element (which may be located at theposition indicated at 108 d in FIGS. 3A-D). In this manner, amultiplexed light is separated into its component channels.

The OAE may comprise an optical component, or a plurality of coupledoptical components, that is configured to allow at least two directionalchanges at different positions along a beam path. For instance, the OAEmay comprise two coupled non-parallel and non-coplanar surfaces whichprovide reflective, refractive and/or diffractive elements for changingthe direction of a beam path. A first directional change may occur at afirst position when the beam hits a first reflective, refractive and/ordiffractive surface. A second directional change may occur at a secondposition (spaced apart from the first position) when the beam hits asecond reflective, refractive and/or diffractive surface. In particular,a prism may be used as an OAE in exemplary embodiments. The OAE may beconfigured to provide four degrees of freedom which affect the directionof the beam (out of six axes of movement—x, y and z axes and rotationaround x, y and z axes) as described further below.

As a result, the OAE may be configured to provide an output beam paththat is non-coplanar with the input beam path. As described below, theuse of an OAE in various embodiments can provide important advantages inthe process of aligning optical components. In alternate embodiments,however, other alignment systems could be used, such as a system withtwo non-coupled reflective surfaces or other separate individuallyaligned optical components.

FIGS. 4-10 illustrate an embodiment of the OAE as a prism. Forillustrative purposes, the Cartesian x-axis, y-axis, and z-axis aredefined as shown in FIGS. 4-10.

FIG. 4 illustrates a top, side, and cross-sectional orthogonal views ofthe prism as the OAE. The top view illustrates the prism 500 along thez-axis; the side view illustrates the prism 500 along the x-axis; andthe cross-sectional view illustrates the prism 500 along the y-axis.FIG. 5 illustrates an isometric view of the prism as the OAE. In FIGS. 4and 5, an emitter 502 provides an emitted beam 510. The emitted beam 510enters the prism 500 and reflects off a first surface 506 at point 514 ato a second surface 508. The beam reflects off the second surface 508 atpoint 514 b and exits the prism 500 as reflected beam 512. The reflectedbeam 512 travels to point 514 c on a receiver 504. The first 506 andsecond 508 surfaces are non-parallel and non-coplanar. FIGS. 6-10illustrate the positioning of a beam with various prism movements. Thex-, y-, and z-axes at the prism 500 and receiver 504 are defined asshown in FIGS. 6-10. FIG. 6 illustrates the positioning of the beam witha prism movement in the x-direction. A movement of the prism 500 alongthe prism x-axis (X_(p)) produces a shift along the receiver x-axis(X_(r)) and a smaller shift along the receiver y-axis (Y_(r)). One ofordinary skill in the art will understand that with the axes as definedabove, the shift of the reflected beam 512 along Y_(r) results from somecoupling along the prism z-axis (Z_(p)), where movement of prism 500along X_(p) results in additional path length for the beam. For example,the prism 500 can be moved such that the emitted beam 510 is reflectedfrom the first surface 506 at point 702 a, reflected from the secondsurface 508 at point 702 b, and travels to point 702 c on the receiver504. For another example, the prism 500 can be moved such that theemitted beam 510 is reflected from the first surface 506 at point 704 a,reflected from the second surface 508 at point 704 b, and travels topoint 704 c on the receiver 504.

FIG. 7 illustrates the positioning of the beam with a prism movement inthe θ_(x) direction. A movement of the prism 500 in the prism θ_(x)direction results in a shift of the reflected beam 512 along Y_(r) androtated in the receiver θ^(x) (θ_(xr)) direction. For example, the prism500 can be moved such that the emitted beam 510 is reflected from thefirst surface 506 approximately at point 514 a, reflected from thesecond surface 508 at approximately point 514 b, and travels either topoint 802 or 804 on the receiver 504. Since the point 514 a on the firstsurface 506 is moved a small amount compared to the movement of thepoints 802 or 804 on the receiver 504, the angle of θ_(xr) is changed.Thus, there are small changes in the points 514 a and 514 b whenrotating about the prism θ_(x) axis (θ_(xp)).

FIG. 8 illustrates the positioning of the beam with a prism movement inthe z-direction. A movement of the prism 500 along Z_(p) results in ashift of the reflected beam 512 along Y_(r). For example, the prism 500can be moved such that the emitted beam 510 is reflected from the firstsurface 506 at point 902 a, reflected from the second surface 508 atpoint 902 b, and travels to point 902 c on the receiver 504. For anotherexample, the prism 500 can be moved such that the emitted beam 510 isreflected from the first surface 506 at point 904 a, reflected from thesecond surface 508 at point 904 b, and travels to point 904 c on thereceiver 504.

FIG. 9 illustrates the positioning of the beam with a prism movement inthe θ_(z) direction. A movement of the prism 500 in the prism θ_(z)direction (θ_(zp)) results in a shift of the reflected beam 512 alongthe X_(r), and about the receiver θ_(y) (θ_(yr)) direction and a smallershift along the Y_(r) and about the θ_(r) direction. For example, theprism 500 can be moved such that the emitted beam 510 is reflected fromthe first surface 506 at point 1002 a, reflected from the second surface508 at point 1002 b, and travels to point 1002 c on the receiver 504.For another example, the prism 500 can be moved such that the emittedbeam 510 is reflected from the first surface 506 at point 1004 a,reflected from the second surface 508 at point 1004 b, and travels topoint 1004 c on the receiver 504.

For the sake of completeness, FIG. 10 illustrates the positioning of thebeam with a prism movement in the prism y-direction and in the prismθ_(y) (θ_(yp)) direction. A movement of the prism 500 in the prismy-direction (Y_(p)) and the θ_(yp) direction results in a small shift inthe reflected beam 512.

Thus, the prism 500 provides four degrees of freedom which affect thereflected beam 512: translation of the reflected beam 512 along X_(r),translation of the reflected beam 512 along Y_(r), rotation of thereflected beam 512 about θ_(xr), and rotation of the reflected beam 512about θ_(yr). If the receiver 504 is an optical fiber, then thetranslations along X_(r) and Y_(r) center the reflected beam 512 on theface of the fiber, and the rotations about θ_(xr) and θ_(yr) ensuresthat the reflected beam 512 enters the fiber perpendicular to thefiber's face. With these four degrees of freedom which affect thereceiver beam 512, the prism 500 can align light beams between twolocations.

Although the axes are defined as illustrated in FIGS. 4-10, they can bedefined in other ways.

The OAE 106 allows for significant advantages over conventional methodsin the manufacturing of optical devices. It allows the optical elementsin a device, other than the OAE 106, to be placed and fixed in placewithout substantially compensating for optical alignment errors, such asusing a reference surface or a vision system, or some other system ormethod that does not substantially compensate for optical alignmenterrors. The OAE 106 is inserted into the beam path, and the beam isaligned to a desired beam path, where alignment of the beam pathsubstantially compensates for cumulative alignment errors in the beampath. This greatly increases the ease in the manufacturing of opticaldevices, especially for devices with numerous optical elements, andlowers the cost of manufacturing. Because only the OAE 106 needs to beaccessed and moved for alignment, the size of the device can be smaller.Also, the tolerances of the placement of optical elements are alsoincreased, and the optical elements do not require special features foralignment.

The OAE 106 may be used to manufacture many different optical devices.For example, it can be used to manufacture a single or multi-channelmultiplexer, demultiplexer, transmitter, receiver, or transceiver, orany combination thereof. The alignment and manufacturing method usingthe OAE 106 is further described in the above referenced co-pending U.S.patent application Ser. No. 09/916,624 incorporated herein by referencein its entirety.

FIGS. 11A-11E illustrate a top isometric, bottom isometric, top, bottom,and side views, respectively, of another embodiment of a core of thedevice. Core 1100 has a prismatic shape and is composed of metal,ceramic, plastic or any other material or combination of materials thatprovides a rigid frame with a coefficient of thermal expansioncompatible with the desired specifications. The core 1100 comprisesthree side faces 1102, 1104, 1106, and two end faces 1108, 1110. Thecore 1100 also comprises a cut face 1112. The function of the cut face1112 is the same as the cut face 212 of the core 200. Traversing fromthe cut face 1112 to a first location on the face 1106 is a first bore1116. Traversing from the first bore 1116 to a second location on theface 1106 is a second bore 1118. The core 1100 also comprises additionalbores 1114 that traverse from the faces 1102 and 1104 to the face 1106.The location of the bores 1114 a-1114 d, 1116, and 1118 match the pathof a beam traversing through a multi-channel device. The bores 1114a-1114 d, 1116, 1118 will be further described below.

FIGS. 12A-12D illustrate a top isometric, bottom isometric, top, andbottom views, respectively, of an embodiment of a multiplexing devicewith an embodiment of the core. In this embodiment, the multiplexingdevice uses light sources 108 a-d that are passive. The filters 104 aand 104 c (not shown) are coupled to the side face 1102 of the core 1100at the location of the bores 1114 a and 1114 c, respectively. Thefilters 104 b and 104 d (not shown) are coupled to the side face 1104 ofthe core 1100 at the location of the bores 1114 b and 1114 d,respectively. The filters 104 a-104 d are not illustrated in FIGS.12A-12D so that the bores 1114 a-1114 d can be seen. A first mirror 1202is coupled to the cut face 1112 at the location of the first bore 1116,and a second mirror 1206 is coupled to the side face 1106 at thelocation of the bores 1114 a-1114 d on that face (see FIG. 12B). TheOAE's 106 a-106 d are then placed proximate to the core 1100 so thatthey are optically coupled to their respective filters 104 a-104 d.

Light source 108 d emits λ₄ to the OAE 106 d, which redirects λ₄ to thefilter 104 d. Filter 104 d transmits λ₄ through the bore 1114 d to thesecond mirror 1206, which in turn reflects λ₄ through the bore 1114 c tothe filter 104 c. Light source 108 c emits λ₃ to the OAE 106 c, whichredirects λ₃ to the filter 104 c. The filter 104 c transmits λ₃ andreflects λ₄ through the bore 1114 c to the second mirror 1206. Thesecond mirror 1206 in turn reflects λ₃-λ₄ through the bore 1114 b to thefilter 104 b. Light source 108 b emits λ₂ to the OAE 106 b, whichredirects λ₂ to the filter 104 b. Filter 104 b transmits λ₂ and reflectsλ₃-λ₄ through the bore 1114 b to the second mirror 1206. The secondmirror 306 in turn reflects λ₂-λ₄ through the bore 1114 a to the filter104 a. Light source 108 a emits λ₁ to the OAE 106 a, which redirects λ₁to the filter 104 a. The filter 104 a transmits λ₁ and reflects λ₂-λ₄through the bore 1114 a to the second mirror 1206. The second mirror1206 in turn reflects λ₁-λ₄ through the first bore 1116 to the firstmirror 1202, which in turn reflects λ₁-λ₄ through the second bore 1118to the output element 1204. In this manner, λ₁, λ₂, λ₃, and λ₄ aremultiplexed into the same output element 1204.

A demultiplexing device may use a similar structure by replacing lightsources 108 a-d with four output elements and by replacing the outputelement 1204 with an input element. A multiplexed light with λ₁-λ₄ maybe provided by the input element (which may be located at the positionindicated at 1204 in FIGS. 12A-D) to the first bore 1116 to the firstmirror 1202. The first mirror 1202 reflects the light through the secondbore 1118 to the second mirror 1206, which in turn reflects the lightthrough the bore 1114 a to the filter 104 a. Filter 104 a transmits λ₁to the OAE 106 a while reflecting λ₂-λ₄ through the bore 1114 a to thesecond mirror 1206. The OAE 106 a redirects λ₁ toward the first outputelement (which may be located at the position indicated at 108 a inFIGS. 12A-D), while the second mirror 1206 reflects λ₂-λ₄ to the filter104 b through the bore 1114 b. The filter 104 b transmit λ₂ to the OAE106 b while reflecting λ₃-λ₄ through the bore 1114 b to the secondmirror 1206. The OAE 106 b redirects λ₂ to second output element (whichmay be located at the position indicated at 108 b in FIGS. 12A-D), whilethe second mirror 1206 reflects λ₃-λ₄ through the bore 1114 c to thefilter 104 c. The filter 104 c transmits λ₃ to the OAE 106 c whilereflecting λ₄ through the bore 1114 c to the second mirror 1206. The OAE106 c redirects λ₃ to the third output element (which may be located atthe position indicated at 108 c in FIGS. 12A-D), while the second mirror1206 reflects λ₄ through the bore 1114 d to the filter 104 d. The filter104 d transmits λ₄ to the OAE 106 d. The OAE 106 d redirects λ₄ to thefourth output element (which may be located at the position indicated at108 d in FIGS. 12A-D). In this manner, a multiplexed light is separatedinto its component channels. The locations of the bores 1114 a-1114 d,1116, and 1118 thus match the path of a beam traversing through thedemultiplexing device.

In an exemplary embodiment, the filters 104 a-104 d and mirrors 1202 and1206 are coupled to the core 1100 by first deburring the core 1100 andcleaning it in a solvent. The core 1110 is then placed in a jig thatholds the appropriate face approximately horizontally. This jig isplaced on a hot plate. One of the components, such as filter 104 a, isplaced in the appropriate location on the core 1100. A spring clip maybe used to hold the filter 104 a against the surface of the core 1100.Preferably, the filter 104 a mates closely to the surface of the core1100. With the filter 104 a held in place, a fiber tool is dipped intoan epoxy to obtain a droplet of epoxy on the tip of the fiber tool. Thisdroplet of epoxy is then touched to the contact between the filter 104 aand the core 1100. The epoxy then “hot wicks” into the contiguous areaof the contact. Due to the viscous properties of the epoxy at the heatedtemperature, the epoxy travels, or “wicks”, throughout the contact areaand fills in the gaps between the filter 104 a and the core 1100. Aboutthe optimal amount of epoxy will fill the contact area withoutexcessively extruding from the contact area. By hot wicking, inadvertenttilting of the filter 104 a due to the uneven thickness of the appliedepoxy is reduced. A feature of hot wicking is that the epoxy does notcover the area of the filter 104 a over its bore 1114 a. The epoxy isthen allowed to cool, and the process is repeated for the remainingcomponents. In this embodiment, the first mirror 1202 is first epoxiedto the core 1100, then each filter 104 a-104 d, and then the secondmirror 1206.

In an exemplary embodiment, an epoxy such as Zymet F-711 is used tocouple the filters 104 a-104 d and mirrors 1202 and 1206 to the core1100. However, other epoxies can also be used. Preferably, the epoxy hashigh temperature stability, low viscosity, high strength, and highmoisture absorption.

FIGS. 13A-13C illustrate an isometric, top, and front views,respectively, of an embodiment of a chassis for the multi-channeldevice. The chassis 1300, (which together with the core provides a“frame” for the device in this embodiment), comprises a top face 1302,bottom face 1304, first side face 1310, second side face 1312, a firstend face 1306, and a second end face 1308. The chassis 1300 comprises ahole 1314 that traverses from the first end face 1306 to the second sendface 1308. The core 200 or 1100 resides within the hole 1314 (shown inFIGS. 13A-C with demultiplexer components which include output elements109 a-d and an input element 1305; for a multiplexer device, lightsources 108 a-d and output element 304 or 1204 may be substituted). Thechassis 1300 also comprises holes 1316 in the top face 1302 thattraverse to the hole 1314. The bottom face 1304 also comprises holes1320 that traverse to the hole 1314. The OAE's 106 a-106 d reside withinthe holes 1316, and the output elements 109 a-109 d reside within theholes 1320. In addition, the chassis 1300 comprises holes 1318 foralignment of pins (not shown), used to help position the core. In thisembodiment, if core 200 is used, the filters 104 a-104 d and mirrors 302and 306 are first coupled to the core 200, as illustrated in FIGS.3A-3D, using the hot wicking method described above. If core 1100 isused, the filters 104 a-104 d and mirrors 1202 and 1206 are firstcoupled to the core 1100, as illustrated in FIGS. 12A-12D, using the hotwicking method. Then, the core/filter/mirror assembly is placed withinthe hole 1314. The output elements 109 a-109 d are also placed in theirrespective holes 1320. The output elements 109 a-109 d can be pressfitted, interference fitted, thermal fitted, epoxied or soldered withinthe hole 1320, or held in place using any other type of fastening orfixing method.

In an exemplary embodiment, assume that the components 109 a-109 d arecollimators. The collimators should be placed as close as possible,while allowing for the tolerances of each component. This will minimizethe amount of epoxy required to affix them to the chassis 1300.Preferably, the length of engagement of the collimators into the chassis1300 should be maximized to reduce the angular effects of changes inepoxy geometry. A symmetrical end stop can be provided to ensureconsistent depth of insertion without causing any asymmetrical forces.The collimators 109 a-109 d are inserted into its respective hole up tothe end stop.

The collimators 109 a-109 d are then held in place as co-linearly to itshole as possible to help with symmetry of adhesive. Once inserted, thecollimator/chassis assembly should be heated smoothly and evenly. Thehigher the temperature, the lower the viscosity, the faster the wicking,and the faster the curing. However, if the temperature is too high, itmay cause curing before the epoxy wicks or the epoxy will break down.

Once the assembly is heated, a very small amount of epoxy is applied tothe contact between the collimators 109 a-109 d and the chassis 1300.The epoxy will naturally wick to fill the spaces of the contact. A glassfiber or very thin needle can be used to apply the epoxy. The epoxy isthen cured at the applicable temperature for the appropriate amount oftime, as determined by the epoxy used. The assembly is then cooled.Next, the OAE's 106 a-106 d are placed within the holes 1316. Each OAE106 a-106 d is adjusted, as described above with FIGS. 4-10, to achievealignment for its respective channel. Once alignment is achieved, eachOAE 106 a-106 d is coupled to the chassis 1300. Each OAE can be coupledto the chassis 1300 using any method of fastening or fixing includingbut not limited to soldering or gluing.

In an exemplary embodiment, the fit between the OAE 106 a-106 d shouldbe as close as possible, while allowing for the tolerances of eachcomponent. This will minimize the amount of epoxy required to affix themto the chassis 1300. For the OAE 106 a-106 d, space for movement of theOAE 106 a-106 d during the alignment process is also required. This willrequire additional epoxy. Once an OAE, such as OAE 106 a, is aligned foroptimum performance, a fixture holds the OAE 106 a in place as securelyas possible. The OAE 106 a/chassis 1300 assembly is heated, preferablysmoothly and evenly. A very small amount of epoxy is applied to thecontact between the OAE 106 a and the chassis 1300. The epoxy willnaturally wick to fill the tight spaces of the contact. Since the amountof space between the OAE 106 a and the chassis 1300 is relatively large,a higher viscosity or filled epoxy may be needed. The epoxy is cured atthe applicable temperature for the appropriate amount of time. Thefixture can then be removed since the epoxy is cured. The assembly isthen cooled.

In an exemplary embodiment, to couple the core 1100 to the chassis 1300,the fit between the core 1100 and chassis 1300 should be as stable aspossible. For example, the core 1100 can be held in a v-groove withepoxy. A stable fixture, which holds the core 1100 in place with aspring, can be used. This maintains a consistent pressure on theconstraining geometry while reducing other forces. The core/chassisassembly is then heated, preferably smoothly and evenly. A very smallamount of epoxy is applied to the contact between the core 1100 and thechassis 1300. The epoxy naturally wicks to fill the spaces of thecontact. The epoxy is cured at the applicable temperature for theappropriate amount of time. The assembly is then cooled.

The chassis 1300 may be sealed with covers (not shown) on the end faces1306 and 1308 and on the top 1302 and bottom faces 1304. These coverscan be affixed to the chassis 1300 with epoxy, solder, or some othermethod.

Several configurations may be used to couple an OAE 106 a-106 d to thechassis 1300 while within the holes 1316 of the chassis 1300. FIGS.14A-14C illustrate an isometric, top, and side view of a bowtieconfiguration of hole 1316 in the chassis, which allows OAE 106 torotate and translate within the hole 1316. The OAE 106 is aligned intoposition and fixed or fastened to the chassis 1300 at two locations1402.

FIGS. 15A-15E illustrate two top isometric views, two bottom isometricviews, and a side view, respectively, of a graduation cap method foradjusting the OAE in the chassis for the device. In this method, theholes 1316 in the chassis 1300 comprise walls 1504 (FIG. 15A) to which acap 1506 (FIG. 15B) may couple. FIG. 15C illustrates the cap 1506 inmore detail. The bottom of the cap 1506 comprises tabs 1508 which canhold onto an OAE 106. FIG. 15D illustrates the cap 1506 with an OAE 106.The cap 1506 with the OAE 106 is rotated during the alignment process.The OAE 106 may also be translated between the tabs 1508. Once alignmentis achieved, the OAE 106 is coupled to the cap 1506, and the cap 1506 iscoupled to the wall 1504.

FIG. 15F is a block diagram of an exemplary system 1550 for aligning theOAE in an optical device in accordance with an embodiment of the presentinvention. The exemplary system includes a computer system 1552, acontroller 1554, an RS-232 cable 1556 or other communications interfacebetween the controller and the computer system, a 6-axis stage withmotor 1556, optical components to be aligned 1558, and an optical powermeter 1560. The controller, 6-axis stage with motor and optical powermeter may be provided as an integrated system or as separate componentsand may be operatively connected using a system bus, cables or othercommunications interface. The 6-axis stage with motor 1556 may bemechanically coupled to the cap 1506 for moving the OAE 106 foralignment (or another device for manipulating the OAE such as thosedescribed in FIGS. 16A-C, 17A-D and 18A-B below). The computer system1552 provides commands and alignment algorithms to the controller 1554across cable 1556. The controller 1554 controls the axis stage withmotor 1556 to move one of the optical components for alignment inaccordance with the algorithm from the computer system 1552. Forinstance, the OAE 106 may be moved relative to the chassis and core foralignment or the chassis could be moved relative to an OAE. In addition,the system 1550 may be used to align mirrors, filters, lens, collimatorsand other components by moving them or moving the chassis in accordancewith an alignment algorithm. In an exemplary embodiment, variouscomponents may be grossly aligned and fixed in position and then the OAEmay be aligned to correct for any errors.

The computer system 1552 executes software which includes a graphicaluser interface (GUI) 1562 which allows the user to select algorithms andcommands to send to the controller, alignment algorithms 1564, a driveraccess layer 1566 and driver software 1568. In an exemplary embodiment,the controller may be a Polytec PI F206 system and the driver softwaremay be HEXDLL software available from Polytec. Other controllers may beused in alternate embodiments, such as other controllers available fromPolytech, Burleigh, AutoOptics, Newport and GOC. As the opticalcomponent is moved, the optical power meter 1560 detects the opticalpower and provides feedback to the controller 1554. The controller movesthe optical component across a range of positions in accordance with thealignment algorithms in order to detect changes in the optical power.The alignment algorithms may include a spiral search algorithm to findan initial start position for alignment with power above a certainthreshold and a hill climb algorithm for finding a position withoptimized lighting. A surface fitting approach, raster scan or otheralgorithms may also be provided. Exemplary alignment methods used forthe OAE 106 are further described in the above referenced co-pendingU.S. patent application Ser. No. 09/916,624 incorporated herein byreference in its entirety.

The alignment algorithms may be used to incrementally step throughdifferent positions along an axis of motion. The axis expected to havethe greatest impact on alignment may be used first, followed by movementalong less significant axes. The process may be iterated until a desiredalignment has been achieved. The following are examples of definitionsfor the axes that be used for the alignment system: the X-axis moveshorizontally left to right along the center line of the stage; theY-axis moves horizontally front to back; the Z-axis moves vertically upand down; the Pitch-axis or U-axis rotates about the X-axis; theYaw-axis or V-axis rotates about the Y-axis; and the Roll-axis or W-axisrotates about the Z-axis.

In the following, the algorithm to align the XYZ position of an opticalcomponent is described. The UVZ position may be similarly adjusted.First, a scan search algorithm is used to find initial light couplingposition for alignment. A spiral scan or raster scan in X and Y may beused to find a power reading above some threshold. The search continuesuntil the threshold is reached or the maximum radius has been searched.The threshold value may be specified from the GUI. If the thresholdcould not be reached, Z-axis gets stepped and the XY scan search runsagain. This process repeats until the threshold is reached. After thethreshold is reached, a 2-dimension auto alignment algorithm is run toalign XY position to the maximum power. The 2-dimension auto alignmentalgorithm may be specified from the GUI. The choices may include: SpiralScan, Raster Scan, XYX Hill Climb, and YXY Hill Climb.

For the Hill Climb algorithm, the following three parameters arespecified from the GUI: initial step size, number of check points, andnumber of iterations. The “step size” is a parameter that determines themagnitude of motion along each axis. “Check points” is the parameterthat specifies the number of steps the algorithm takes past each maximumpoint in order to check to see if the hill would begin to rise again ornot. After locating the absolute peak of the hill, the Hill Climberreduces the size of its step size by a factor of two and goes climbingin the reverse direction. The Hill Climber repeats the process andpasses over the hill as many times as indicated by a parameter referredto as “iterations”. This is done in order to fine tune the alignment.Upon arrival to the top of the peak the next time, the Hill Climber nolonger crosses over it and rests at the top. Once the Hill Climb processis completed along one axis, it is repeated along the other axis andafter that once again along the first axis.

FIG. 15G is a flow chart illustrating an exemplary Hill Climb algorithmthat may be used in connection with embodiments of the presentinvention. The axes may be ordered based on the amount of impactmovement along the axis has on the beam position (with the first axishaving the greatest impact). At steps 1561, 1562 and 1563, a Hill Climbalgorithm is performed for the first axis, second axis and then thefirst axis again. The Hill Climb alignment for each axis determines theposition along the axis with the optimum power. This position is thenused as the starting position for the Hill Climb alignment along thenext axis. Only three axes may be adjusted for alignment of componentswith limited degrees of freedom, such as a mirror. For these componentsa Hill Climb algorithm is performed for the third axis at step 1565 andthen steps 1561, 1562 and 1563 are repeated (as indicated at step 1569).

Other components, such as an OAE, may use a four axis alignment. If afour axis alignment is to be performed (as indicated at step 1564), thethird and fourth axes are aligned using a Hill Climb algorithm asindicated at steps 1566 and 1567. The Hill Climb for the third axis isthen performed again at step 1568. Steps 1561, 1562 and 1563 are thenrepeated (as indicated at step 1569).

At step 1570, the step size is reduced. In one exemplary method, thestep size is reduced by one half for components other than lenses orOAEs (such as mirrors and collimators). The step size for alignment of alens or OAE is reduced by one fifth. The process then iterates based onthe “iterations” parameter.

In an exemplary embodiment of a Hill Climb alignment method for an OAE,the first axis is the U axis, the second axis is the V axis, the thirdaxis is the X axis and the fourth axis is the Z axis. The step size forthe translational axes (X and Z) is 0.1 mm. The step size for therotational axes (U and V) is 0.1 degrees. In this embodiment, a singleiteration is used and the step size is not reduced. In anotherembodiment, the initial step sizes are 1 mm and 1 degree and the stepsizes are reduced over several iterations.

After the above Hill Climb method is performed, a fine alignment may beperformed as illustrated in FIG. 15H. While the Hill Climb finds aposition with optimal power, the power may drop off much more rapidly bymovement in one direction along the axis rather than the otherdirection. In such cases, it may be desirable to center the alignmentpoint in between points along the axis where the power starts to dropbelow a desired threshold (such as 99% of the optimum power found usingthe Hill Climb method). As shown at step 1571 in FIG. 15H, the HillClimb method is first completed to determine an initial optimumalignment position. At step 1572, the component is then moved in a firstdirection along the first axis. At step 1573, a check is made to see ifthe power is still above 99% of the initial optimum. If so, the positionis recorded at 1574 and another step is taken along the axis is taken asshown at 1572. This continue until the power drops below 99% of optimum.Once the power drops below 99%, the method moves back to the lastposition that was above 99% as shown at 1575. This is recorded as anaxis point (X1) at step 1576. This marks the last position before thepower drops below the 99% threshold due to movements in the firstdirection along the first axis.

Then, the algorithm steps along the axis in the second direction asshown at 1577 which may be opposite the first direction. A check is madeat step 1578 to see if the power remains above 99% of optimum. If so,the position is recorded at 1579 and another step is taken along theaxis in the second direction. This is repeated until the power fallsbelow 99% of optimum. Once the power drops below 99%, the method movesback to the last position that was above 99% as shown at 1580. This isrecorded as an axis point (X2) at step 1581. This marks the lastposition before the power drops below the 99% threshold due to movementsin the second direction along the first axis. At step 1582, the midpoint between X1 and X2 is calculated (i.e., the mid point between thepositions along the axis where the power falls below 99% of optimum).This allows for the same alignment error in either direction before thepower drops below the threshold. The fine alignment is then repeated forthe other axes. The fine alignment repeats in the same manner as theHill Climb algorithm. The first axis and second axis are aligned andthen the first axis is aligned again. For a three axis alignment, thethird axis is then aligned and alignment of the first axis, second axisand first axis are then repeated again. For a four axis alignment, thethird axis and fourth axis are aligned. Then the third axis is alignedagain. Alignment of the first axis, second axis and first axis are thenrepeated again. The mid-point position determined in each alignment stepis used as the starting position for fine alignment along the next axis.

In one embodiment of a fine alignment method, the step size is the sameas the final step size used for the Hill Climb method. For instance, thestep size may be 0.1 mm for translational axes (X, Y and/or Z) and 0.1degrees for rotational axes (U, V and/or W). In an exemplary embodimentof a fine alignment method for an OAE, the first axis is the U axis, thesecond axis is the V axis, the third axis is the X axis and the fourthaxis is the Z axis.

For the Raster Scan algorithm, the following three parameters may bespecified from the user interface: initial step size, number of scanpoints, and number of iterations. The “step size” determines themagnitude of motion along each axis. “Scan points” is the parameter thatspecifies the number of steps the algorithm takes along each axis, whichdefines the area of scan. The Raster Scanner first does a raster scanusing the initial step size and scan points and moves to the position ofmaximum power. Then it may optionally reduce the step size by half orsome other desired amount and repeat the raster scan using the new stepsize and the original scan points over the square area centered at theposition of maximum power. The process is repeated as many times asindicated by a parameter referred to as “iterations”.

For the Spiral Scan algorithm, the following three parameters may bespecified from the user interface: initial spiral radius, angleseparation, number of scan points, and number of iterations. The “spiralradius” determines the magnitude of the radius for the spiral function.The “angle separation” determines the increment of angle from one scanpoint to the next. “Scan points” is the parameter that specifies thenumber of steps the algorithm takes along the spiral curve. The “angleseparation” and “scan points” together define the area of scan. TheSpiral Scanner will first do a spiral scan using the initial step sizeand scan points and move to the position of maximum power. Then it mayoptionally reduce the step size by half or some other desired amount andrepeat the spiral scan using the new step size and the original scanpoints over the circular area centered at the position of maximum power.The angle separation remains the same for each iteration. The process isrepeated as many times as indicated by a parameter referred to as“iterations”.

After 2-dimensional auto alignment is done at one position along Z-axis,the Z-axis is single stepped followed by another run of 2-dimensionalauto alignment to maximize the optical power. Both directions in Z-axiswill be checked to determine the direction of further movement alongZ-axis. This is repeated until power would not maximized by any furthermovement along the Z-axis. The following two parameters may be specifiedfrom the user interface for Z-axis movement: initial step size andnumber of iterations. The “step size” determines the magnitude of motionalong Z-axis. “Iterations” is the number of iterations to be repeatedfor Z-axis alignment described above. The step size will be reduced byhalf for each iteration.

In an exemplary spiral search, the step size is 0.1 mm for movementalong the X, Y and Z axes. The X and Y axes are each stepped 25 times ina spiral fashion for a given plane along the Z axis. The Z axis is thenstepped and the process is repeated. The process is continued for thedesired number of iterations along the Z axis. In this exemplaryembodiment, only one iteration is performed and the step size is notreduced. In another exemplary embodiment, the initial step size is 1 mmand is reduced over several iterations. In another exemplary embodiment,the U, V and/or W axes may be stepped angularly with a step size of 0.1degrees or other desired step size.

A surface fitting approach may also be used. Emerging light coming outof the optical components 1558 form a surface with a particular area inthe surface having maximum intensity. The surface fitting approach firstdoes a spiral scan search to collect all the points traversed to findthe threshold light area. The collected point are fit into a surfacewith the generic equation as follows: Z=f (X,Y) where Z axisco-ordinates are function of X (coordinates in x-axis) and Y(coordinates in y-axis). The function can be polynomial. Once thefunction has been obtained by doing surface fitting, the maxima for thesurface can be obtained by applying the maxima-minina theorem on thefunction and by obtaining the first and second partial derivative.

FIGS. 16A-16C illustrate an isometric, side, and top views,respectively, of yet another embodiment of a system for allowingadjustment of OAE and coupling to the chassis. The system may be used toadjust the OAE in the alignment system described above. In this system,the OAE 106 is held by two partially spherical parts 1604 and 1606. Thepartially spherical parts 1604 and 1606 abut against the chassis 1300within the hole 1316 at the curved surfaces of the partial spheres. Thepartially spherical shapes of the parts 1604 and 1606 allow the OAE 106to be rotated and translated during the alignment process. Oncealignment is achieved, the OAE 106 is coupled to the parts 1604 and1606, and the parts 1604 and 1606 are coupled to the chassis 1300.Alternatively parts 1604 and 1606 can be coupled to the OAE prior toalignment of the OAE 106.

FIGS. 17A-17D illustrate a top, top isometric, top cross-sectional, andside cross-sectional views, respectively, still another embodiment of asystem for allowing adjustment of an OAE and coupling to the chassis.The system may be used to adjust the OAE in the alignment systemdescribed above. In this system, the OAE 106 abuts against a partiallyspherical part 1704, which abuts against the chassis 1300 within thehole 1316. The OAE 106 may be made to abut the partially spherical part1704 by another part such as a spring (not shown). The partiallyspherical part 1704 allows the OAE 106 to be rotated and translatedduring the alignment process. Once alignment is achieved, the sphericalpart 1704 is coupled to the chassis 1300, and the OAE 106 is coupled tothe spherical part 1704. Alternatively spherical part 1704 can becoupled to the OAE prior to alignment of the OAE 106.

FIGS. 17E-17F illustrate a top and side cross-sectional view,respectively, of another embodiment of a system for allowing adjustmentof an OAE and coupling to a chassis. The system may be used to adjustthe OAE in the alignment system described above. In this system, a metalplate 1706 abuts against the chassis 1300 within the hole 1316. The OAE106 is coupled to the partially spherical part 1704. The plate 1706and/or part 1704 are coated with a magnetizable material, such as gold,or be composed of magnetizable material. The part 1704 is then heldagainst the metal plate 1706 by a magnet (not shown). The OAE 106 canthen be rotated and translated during the alignment process. Oncealignment is achieved, the partially spherical part 1704 is coupled tothe metal plate 1706.

FIGS. 17G-17H illustrate a top and side cross-sectional view,respectively, of still another embodiment of a system for allowingadjustment of an OAE and coupling to a chassis. The system may be usedto adjust the OAE in the alignment system described above. In thissystem, two metal plates 1706 and 1710 abut against the chassis 1300within the hole 1316. The OAE 106 is coupled to two partially sphericalparts 1704 and 1708. The two parts 1704 and 1708 are then held againstthe metal plates 1706 and 1710 by a magnet (not shown), as describedabove with FIGS. 17E and 17F, or by interference. The OAE 106 can thenbe rotated and translated during the alignment process. Once alignmentis achieved, the partially spherical parts 1704 and 1708 are coupled tothe metal plates 1706 and 1710, respectively.

FIGS. 18A-18B illustrate side views of yet another embodiment of asystem for allowing adjustment of an OAE and coupling to a chassis. Thesystem may be used to adjust the OAE in the alignment system describedabove. In this system, the OAE 106 is coupled to two partially sphericalparts 1802 and 1804. The OAE 106 is then rotated and translated duringthe alignment process. During alignment, a two-pronged spring 1806 isheld open so that the parts 1802 and 1804 are unclamped. (FIG. 18A) Oncealignment is achieved, the spring 1806, which is coupled to or formedfrom the chassis 1300 with the chassis hole 1306, is released to clampthe parts 1802 and 1804, and the OAE 106. (FIG. 18B)

In other embodiments, the optical components 108 a-108 d include but arenot limited to one or more, or a combination of a fiber or fibercollimator laser, a TO-38 laser package, a TO-56 laser package, a lasercan package, a detector, a TO-42 detector package, a TO-56 detectorpackage, a waveguide input or output from or to another embodiment ofthe device or any other optical system or subsystem. The devicecomprises light sources, such as lasers, as the optical components 108a-108 d.

FIG. 18C illustrates an embodiment of the device with a fiber support.The components 108 a-108 d are each optically coupled to an opticalfiber (not shown), typically via a lens (not shown). The connectionpoint 1812 between the lens and the fiber may be subject to strains dueto the handling of the fibers. To reduce this strain, a fiber support1810 is coupled to the chassis 1300. The support 1810 holds the fibersrigidly with respect to the chassis 1300. The support 1810 comprises agroove 1814 for the input/output fiber and grooves 1816 for the fibersoutput/input channel fibers. The support 1810 routes the fibers into anappropriate order at the exit of the module 150 (See FIG. 1). The fibersare held in place by a clip (not shown) that resides within a fiber clipslot 1818.

In addition to reducing strain at the fiber/lens joint, the fibersupport 1810 uses a reasonable bend radius in routing the fibers, iseasy to assemble, allows for the snapping of the fibers into the grooves1814 and 1816, and allows for a small overall package while allowing asignificant straight length of fiber exiting the device.

The use of OAEs, different core configurations and folded beam paths maybe used in alternate embodiments of a multiplexing device ordemultiplexing device to allow advantageous positioning of active andpassive elements in the devices. In addition, in some embodiments, thebeams between the components are transmitted in free space (instead ofusing a fiber or optical guide) which allows a compact design to be usedfor a wide variety of configurations. For example, it may be desirableto use active light sources (for a multiplexer device) or outputelements (for a demultiplexer device) that have electrical leads whichneed to be mounted on a printed circuit board or other surface orinterface. It is desirable in some embodiments to configure the activeelements so all of the leads exit the frame in the same direction (suchas out of the bottom of the device). This facilitates mounting theelectrical leads of the active devices. An active output element for thea composite multiplexed beam (for a multiplexer device) or active inputelement (for a demultiplexer device) may be configured in the samedirection. If the output element for the a composite multiplexed beam(for a multiplexer device) or the input element (for a demultiplexerdevice) is passive (such as an optical fiber), it may be desirable tohave the elements exit the frame out of the sides perpendicular to theactive leads. The folded beam paths, cores and OAEs may be used toposition the various elements so that electrical leads, inputs andoutputs can pass through any desired side of the device as required forthe particular application. The additional embodiments described belowillustrate alternative configurations, including configurations withactive leads aligned with the bottom of the device and an output orinput optical fiber interfacing through a perpendicular side of thedevice.

FIGS. 19A-19C illustrate a top isometric, bottom isometric, and topviews, respectively, of an embodiment of a core for a device. In thisembodiment, the device is active. Core 1900 has a prismatic shape and iscomposed of glass. The core 1900 comprises three side faces 1902, 1904,1906, and two end faces 1908, 1910. The core 1900 also comprises a firstcut face 1912 and a second cut face 1914. The function of the cut faces1912 and 1914 will be described below.

FIGS. 20A-20E illustrate a top isometric, bottom isometric, top, front,and side views, respectively, of yet another embodiment of the device.In this embodiment, the device is active. The filters 104 a and 104 care coupled to the side face 1902 of the core 1900, and the filters 104b and 104 d are coupled to the side face 1904 of the core 1900. A firstmirror 2002 is coupled to the cut face 1912, a second mirror 2004 (seeFIG. 20B) is coupled to the second cut face side face 1914, and a thirdmirror 2006 is coupled to the face 1906. The OAE's 106 a-106 d areplaced proximate to the core 200 so that they are optically coupled totheir respective filters 104 a-104 d.

For example, assuming that the light sources 108 a-108 d are laserspackaged in cans, laser 108 d emits λ₄ to the OAE 106 d, which redirectsλ₄ to the filter 104 d. Filter 104 d transmits λ₄ to the third mirror2006, which in turn reflects λ₄ to the filter 104 c. Laser 108 c emitsλ₃ to the OAE 106 c, which redirects λ₃ to the filter 104 c. Filter 104c transmits λ₃ to the third mirror 2006. Filter 104 c also reflects λ₄to the third mirror 2006. The third mirror 2006 in turn reflects λ₃-λ₄to the filter 104 b. Laser 108 b emits λ₂ to the OAE 106 b, whichredirects λ₂ to the filter 104 b. Filter 104 b transmits λ₂ to the thirdmirror 2006. Filter 104 b also reflects λ₃-λ₄ to the third mirror 2006.The third mirror 2006 in turn reflects λ₂-λ₄ to the filter 104 a. Laser108 a emits λ₁ to the OAE 106 a, which redirects λ₁ to the filter 104 a.Filter 104 a also reflects λ₂-λ₄ to the third mirror 2006. The thirdmirror 2006 in turn reflects λ₁-λ₄ to the first mirror 2002. The firstmirror 2002 reflects λ₁-λ₄ to the second mirror 2004, which in turnreflects λ₁-λ₄ to the output element 2008. In this manner, a multiplexedlight is provided by the device 2000. For an active device, anadditional reflection of the multiplexed light is provided by mirror2004 in order to provide the multiplexed light at a right angle to thechannel beams, while meeting the geometrical constraints of thepackaging of the device 2000. The mirror 2004 is mounted on the cut face1914 to provide this additional reflection. More specifically, themirror 2004 on the cut face 1914 reflects the multiplexed light at theappropriate angle so that it is provided at the correct vertical andhorizontal position, as set forth in the GBIC form factor standard. Ademultiplexer device may be provided by replacing input elements 108a-108 d with output elements which may be detector packages and byreplacing output element 2008 with an input element, as described forthe other embodiments above.

FIGS. 21A-21E illustrate a top isometric, bottom isometric, top, front,and side views, respectively, of yet another embodiment of a core for adevice. In this embodiment, the device is active. Core 2100 has aprismatic shape and is composed of metal. The core 2100 comprises threeside faces 2102, 2104, 2106, and two end faces 2108, 2110. The core 2100also comprises a first cut face 2112 and a second cut face 2114. Thefunctions of the cut faces 2112 and 2114 are the same as the cut faces1912 and 1914 of the core 1900. Traversing from the cut face 2112 to afirst location on the face 2106 is a first bore 2120. Traversing fromthe first bore 2120 to a second location on the face 1106 is a secondbore 2122. The core 2100 also comprises bores 2116 a and 2116 c thattraverse from the face 2102 to the face 2106 and bores 2116 b and 2116d, which traverse from the face 2104 to the face 2106. The function ofthe bores 2116 a-2116 d, 2120, and 2122 will be described below.

FIGS. 22A-22D illustrate a top isometric, bottom isometric, top, andside views, respectively, of still another embodiment of a device shownwith the embodiment of the core described above. In this embodiment, thedevice is active. The filters 104 a and 104 c (not shown) are coupled tothe side face 2102 of the core 2100 at the location of the bores 2116 aand 2216 c, respectively. The filters 104 b and 104 d (not shown) arecoupled to the side face 2104 of the core 2100 at the location of thebores 2116 b and 2116 d, respectively. The filters 104 a-104 d are notillustrated in FIGS. 22A-22D so that the bores 2116 a-2116 d can beseen. A first mirror 2202 is coupled to the first cut face 2112 at thelocation of the first bore 2120, a second mirror 2204 is coupled to thesecond cut face 2114 at the location of the second bore 2122, and athird mirror 2206 is coupled to the side face 2106 at the location ofthe bores 2116 a-2116 d on that face. The OAE's 106 a-106 d are thenplaced proximate to the core 2100 so that they are optically coupled totheir respective filters 104 a-104 d.

For example, laser package 108 d emits λ₄ to the OAE 106 d, whichredirects λ₄ to the filter 104 d. Filter 104 d transmits λ₄ through thebore 2116 d to the third mirror 2206, which in turn reflects λ₄ throughthe bore 2116 c to the filter 104 c. Laser package 108 c emits λ₃ to theOAE 106 c, which redirects λ₃ to the filter 104 c. Filter 104 ctransmits λ₃ and reflects λ₄ through the bore 2116 c to the third mirror2206. The third mirror 2206 reflects λ₃-λ₄ through the bores 2116 b tothe filter 104 b. Laser can package 108 b emits λ₂ to the OAE 106 b,which redirects λ₂ to the filter 104 b. Filter 104 b transmits λ₂ andreflects λ₃-λ₄ through the bore 2116 b to the third mirror 2006. Thethird mirror 2206 reflects λ₂-λ₄ through the bore 2116 a to the filter104 a. Laser 108 a emits λ₁ to the OAE 106 a, which redirects λ₁ to thefilter 104 a. Filter 104 a transmits λ₁ and reflects λ₂-λ₄ through thebore 2116 a to the third mirror 2206. The third mirror 2206 reflectsλ₁-λ₄ through the second bore 2122 to the second mirror 2204. The secondmirror 2204 reflects λ₁-λ₄ through the first bore 2120 to the firstmirror 2202. The first mirror 2202 reflects λ₁-λ₄ to the output element.In this manner, a multiplexed light is provided by the device 2200. Ademultiplexer device may also be provided by substituting the componentsdescribed above.

FIGS. 23A-23E illustrate a top isometric, bottom isometric, top, front,and side views, respectively, of another embodiment of a device. In thisembodiment, the device is active. The chassis 2300 comprises a top face2302, bottom face 2304, first side face 2310, second side face 2312, afirst end face 2306, and a second end face 2308. The chassis 2300comprises a hole (not shown) that traverses from the first end face 2306to the second end face 2308. The core 1900 or 2100, with the filters 104a-104 d and mirrors 2002 or 2202, 2004 or 2204, and 2006 or 2206,resides within the hole. The chassis 2300 also comprises holes 2314 inthe top face 2302 and holes 2316 in the bottom face 2304. The OAE's 106a-106 d reside within the holes 2314, and the light sources 108 a-108 d(or output elements 109 a-d for a demultiplexer) reside within the holes2316. In addition, the chassis 2300 comprises a nozzle bore 2322 forhousing a nozzle 2318, through which the multiplexed light is output orinput. An optical fiber may be coupled to the nozzle 2318. Arms 2320 maybe coupled to the nozzle 2318 to couple the device 2300 to a fiberconnector or other optical system or subsystem. In this embodiment, theOAE's 106 a-106 d can be adjusted in their respective holes 2314 usingany of the adjusting methods illustrated in FIGS. 15A-18B.

Although the embodiments of the cores described above are prismatic,other shapes with the desired surface geometry for the filters andmirrors can be used.

The device can also be provided with a chassis but no core. FIG. 24illustrates a front view of an embodiment of the device without a core.The coreless chassis 2400 comprises a cavity 2404 which traverses fromthe front face 2402 to a back face (not shown). The features of thechassis 2400 within the cavity 2404 are such that the filters 104 a-104d may be coupled onto the features at the appropriate angles. A mirror2406 is also mounted within the cavity 2404. The chassis 2400 furthercomprises holes at its top face (not shown) for the OAE's 106 a-106 d,and holes (not shown) at its bottom face for the light sources 108 a-108d (or output elements 109 a-d for a demultiplexer) and for the outputelement 2408 (or input element for a demultiplexer). Light wouldtraverse between the filters 104 a-104 d, the mirror 2406, and the OAE's106 a-106 d in a manner similar to the filters 104 a-104 d, the secondmirror 306, and the OAE's 106 a-106 d with the first embodiment of thecore 200 described above. The output element 2408 performs the samefunction as output element 304 (FIGS. 3A-3D). A mirror that performs thesame function as the first mirror 304 may also be mounted within thecavity 2404. In this embodiment, a front plate is used, as describedbelow.

FIGS. 25A-25B illustrate a top isometric and bottom isometric views,respectively, of a front plate of the embodiment of the device without acore. In this embodiment, the device is passive. The front plate 2500comprises shelves 2502 on which a mirror 2504 may be mounted at theappropriate angle. The shelves 2502 themselves are mounted onto a plate2506. In this embodiment, the shape of the plate 2506 matches the shapeof the opening of the cavity 2404. The front plate 2500 is then attachedto the coreless chassis 2400 such that the shelves 2502, mirror 2504,and plate 2506 reside within the cavity 2404.

FIGS. 26A-26B illustrate a back and front views, respectively, of theembodiment of the device without the core. In the embodiment, thechassis provides the frame for the device without requiring a separatecore. Once the front plate 2500 is attached to the coreless chassis2400, the elements within the cavity 2404 are in the same orientation asthe corresponding elements for the chassis 300 with a core 200. Becausethe shape of the plate 2506 matches the shape of the opening of thecavity 2404, the front plate 2500 also functions as a plug, such thatwhen the front plate 2500 is soldered onto the coreless chassis 2400, ithelps to create a hermetic seal. Additional plates may be soldered tocover the cavity opening at the chassis's back face and the holes forthe OAE's 106 a-106 d. The light sources 108 a-108 d (or output elementsfor a demultiplexer) and output element 2408 (or an input element for ademultiplexer) may be soldered to the chassis 2402 as well. In thismanner, the device 2400 may be hermetically sealed.

Improved methods and systems for routing and aligning beams and opticalelements in an optical device have been disclosed. The methods andsystems include a multiplexing device, which includes: a plurality oflight sources, wherein each light source provides a beam with a channelin a range of wavelengths; a filter associated with each channel,wherein each filter selects the wavelengths for the respective channel;an output element to receive each channel after it traverses therespective filter; and an OAE associated with each channel, wherein theOAE is configured to provide at least two directional changes in thepath of the beam, wherein the path of the beam input to the OAE may benon-coplanar to the path of the beam output from the OAE.

The methods and systems also include a demultiplexing device, whichincludes: an input element, wherein the input element provides a beamwith a plurality of channels, each channel in a range of wavelengths; afilter associated with each channel, wherein each filter selects thewavelengths for the respective channel; an output element associatedwith each channel, wherein each output element receives the respectivechannel after it traverses the respective filter; and an OAE associatedwith each channel, wherein the OAE is configured to provide at least twodirectional changes in the path of the beam, wherein the path of thebeam input to the OAE may be non-coplanar to the path of the beam outputfrom the OAE.

The OAE can be configured to substantially compensate for the cumulativealignment errors in the beam path. The OAE allows the optical elementsin a device, other than the OAE, to be placed and fixed in place withoutsubstantially compensating for optical alignment errors. The OAE isinserted into the beam path and adjusted. This greatly increases theease in the manufacturing of optical devices, especially for deviceswith numerous optical elements, and lowers the cost of manufacturing.Even as the number of optical elements in the device increases,alignment is still accomplished through the adjustment of the OAE.Because only the OAE needs to be accessed and moved for final alignment,the size of the device can be smaller. Also, the tolerances of theplacement of optical elements are increased, and the optical elements donot require special features for alignment.

The multiplexing device and/or demultiplexing device can reside within astandard form factor, such as the GBIC form factor. The devices fold thepaths of the beams traversing therethrough with a geometry which allowsa small package for the device. The geometry is provided by a core ontowhich filters and mirrors of the device are coupled.

Although the present invention has been described in accordance with theembodiments shown, one of ordinary skill in the art will readilyrecognize that there could be variations to the embodiments and thosevariations would be within the spirit and scope of the presentinvention. Accordingly, many modifications may be made by one ofordinary skill in the art without departing from the spirit and scope ofthe appended claims.

1. A multiplexing device for multiplexing a plurality of channels,wherein each channel contains light within a range of wavelengths, themultiplexing device comprising: a housing; a printed circuit board; anelectrical connector electrically coupled to the printed circuit board;a plurality of transmitters within the housing, each transmitterassociated with one of the channels, wherein each transmitter provides abeam containing the associated channel; each of the transmitters havingelectrical leads mounted to the printed circuit board; a plurality offilters, each filter associated with one of the channels, wherein eachfilter is transverse to the beam containing the associated channel andis configured to select a range of wavelengths which includes theassociated channel; the housing having a front surface substantiallyperpendicular to the printed circuit board; an output collimatorconfigured to receive the channels after the channels are selected bythe associated filters and to provide an optical path for outputting themultiplexed channels through the front surface of the housing.
 2. Thedevice of claim 1, wherein the electrical connector provides anelectrical interface compatible with the Gigabaud Interface Converter(GBIC) interface standard.
 3. The device of claim 1, wherein theelectrical connector provides an electrical interface compatible with aninterface standard selected from the group consisting of a small formfactor (SFF) standard, a small form factor pluggable (SFP) standard, aXenpak (XG), XPAK, XGP2, and XFP.
 4. The device of claim 1, furthercomprising a plurality of optical alignment elements (OAEs), each OAEassociated with one of the channels, wherein each OAE is configured toprovide at least two directional changes in the path of the beamcontaining the associated channel.
 5. The device of claim 1, furthercomprising a plurality of optical alignment elements (OAEs), each OAEassociated with one of the channels, wherein each OAE is configured toprovide at least four degrees of freedom which affect the direction ofthe beam containing the associated channel.
 6. The device of claim 1further comprising a core and a first mirror coupled to the core,wherein: each of the filters is coupled to the core and is configured todirect the associated channel to the mirror; and the first mirror isconfigured to direct each of the channels along a path aligned with theoutput collimator.
 7. A multiplexing device for multiplexing a pluralityof channels, wherein each channel contains light within a range ofwavelengths, the multiplexing device comprising: a housing, the housinghaving a front surface that is substantially planar; a plurality ofinput collimators, each input collimator associated with one of thechannels and configured to provide an optical path for a beam containingthe associated channel into the housing through the front surface; aplurality of filters within the housing, each filter associated with oneof the channels, wherein each filter is transverse to the beamcontaining the associated channel and is configured to select a range ofwavelengths which includes the associated channel; and an outputcollimator configured to receive the channels after the channels areselected by the associated filters and to provide an optical path foroutputting the multiplexed channels through the front surface of thehousing.
 8. The device of claim 7, further comprising a plurality ofoptical alignment elements (OAEs), each OAE associated with one of thechannels, wherein each OAE is configured to provide at least twodirectional changes in the path of the beam containing the associatedchannel.
 9. The device of claim 7, further comprising a plurality ofoptical alignment elements (OAEs), each OAE associated with one of thechannels, wherein each OAE is configured to provide at least fourdegrees of freedom which affect the direction of the beam containing theassociated channel.
 10. The device of claim 7 further comprising a coreand a first mirror coupled to the core, wherein: each of the filters iscoupled to the core and is configured to direct the associated channelto the mirror; and the first mirror is configured to direct each of thechannels along a path aligned with the output collimator.
 11. Ademultiplexing device for demultiplexing a plurality of channels,wherein each channel contains light within a range of wavelengths, thedemultiplexing device comprising: a housing; a printed circuit board; anelectrical connector electrically coupled to the printed circuit board;the housing having a front surface substantially perpendicular to theprinted circuit board; an input collimator configured to input a beamcontaining the plurality of channels through the front surface of thehousing; a plurality of filters, each filter associated with one of thechannels, wherein each filter is transverse to the beam containing theassociated channel and is configured to select a range of wavelengthswhich includes the associated channel; a plurality of receivers, eachreceiver associated with one of the channels, wherein each receiver isconfigured to receive the associated channel after the associatedchannel is selected by the corresponding filter; and each of thereceivers having electrical leads mounted to the printed circuit board.12. The device of claim 11, wherein the electrical connector provides anelectrical interface compatible with the Gigabaud Interface Converter(GBIC) interface standard.
 13. The device of claim 11, wherein theelectrical connector provides an electrical interface compatible with aninterface standard selected from the group consisting of a small formfactor (SFF) standard, a small form factor pluggable (SFP) standard, aXenpak (XG), XPAK, XGP2, and XFP.
 14. The device of claim 11, furthercomprising a plurality of optical alignment elements (OAEs), each OAEassociated with one of the channels, wherein each OAE is configured toprovide at least two directional changes in the path of the associatedchannel.
 15. The device of claim 11, further comprising a plurality ofoptical alignment elements (OAEs), each OAE associated with one of thechannels, wherein each OAE is configured to provide at least fourdegrees of freedom which affect the direction of the associated channel.16. The device of claim 11 further comprising a core and a first mirrorcoupled to the core, wherein: the first mirror is configured to receivethe beam containing the plurality of channels from the input collimatorand to direct the beam containing the plurality of channels along a pathaligned with each of the filters; and each of the filters is coupled tothe core and is configured to receive the beam from the first mirror andto direct the selected channel to the associated receiver.
 17. Ademultiplexing device for demultiplexing a plurality of channels,wherein each channel contains light within a range of wavelengths, thedemultiplexing device comprising: a housing; the housing having a frontsurface substantially perpendicular to the printed circuit board; aninput collimator configured to input a beam containing the plurality ofchannels through the front surface of the housing; a plurality offilters, each filter associated with one of the channels, wherein eachfilter is transverse to the beam containing the associated channel andis configured to select a range of wavelengths which includes theassociated channel; and a plurality of output collimators, each outputcollimator associated with one of the channels, wherein each outputcollimator is configured to receive the associated channel after theassociated channel is selected by the corresponding filter and toprovide an optical path for outputting the channel through the frontsurface of the housing.
 18. The device of claim 17, further comprising aplurality of optical alignment elements (OAEs), each OAE associated withone of the channels, wherein each OAE is configured to provide at leasttwo directional changes in the path of the the associated channel. 19.The device of claim 17, further comprising a plurality of opticalalignment elements (OAEs), each OAE associated with one of the channels,wherein each OAE is configured to provide at least four degrees offreedom which affect the direction of the associated channel.
 20. Thedevice of claim 17 further comprising a core and a first mirror coupledto the core, wherein: the first mirror is configured to receive the beamcontaining the plurality of channels from the input collimator and todirect the beam containing the plurality of channels along a pathaligned with each of the filters; and each of the filters is coupled tothe core and is configured to receive the beam from the first mirror andto direct the selected channel to the associated receiver.